To manage pollutant sources systematically and to predict transformation of water quality reasonably in estuarine reservoir watershed, study of model will be necessarily conduct. In this study, from now model of BASINS/HSPF which can be satisfy all of factor for efficient management of pollution in Hwasung watershed was choose, model was applied after driving off datum of geography, hydrology and water quality and influence of total pollution in Hwasung watershed was analyzed in quantities. In case of Model Efficiency(R2) and %difference, runoff was in the range of 0.62～0.85 and 10.06～19.06 respectably. %difference of Water quality was in the range of -20.47～21.90(CP) and -12.71～15.75(VP). As a result of estimation of pollutant load, JaAn stream was clear than NamYang and EoEun stream but it was appeared that JaAn stream discharged high pollutant load because it has much amount of inflow to estuarine reservoir because of broad watershed area and high length of river. NamYang and EoEun stream was high ranged rates of point source rather than JaAn stream Lots of pollution-causing factory, large scale of housing developments and urbanization caused high discharge of point source. It has felt keenly the necessity of improvement about Unit Load method when was currently evaluated TMDL and it was necessary that evaluation of pollutant load was studied through BASINS/ HSPF.